The continuing violence raises further questions about President Emmerson Mnangagwa’s control over the military, which helped bring him to power 14 months ago, our correspondent adds.

President Mnangagwa has promised that abuses against civilians will not be tolerated.

What has been alleged?

In a blunt statement, the commission said at least eight deaths had been reported since last week, “mostly attributed to use of live ammunition”.

“Armed and uniformed members of the Zimbabwe National Army and the Zimbabwe Republic Police instigated systematic torture.”

It said the torture was “organised” in that security forces targeted men close to where barricades had been erected, and near areas torched by protesters or looted.

The commission detailed reports of security forces entering houses at night and making men, and even boys as young as 11, lie on the ground where they were then beaten.

“The deployment of the army in quelling civilian disturbances leads to loss of life and serious bodily injuries and other human rights violations, yet the government continues to make such deployments,” the statement said.

Other reports say at least 12 people have been killed and scores treated for gunshot injuries.

What is President Mnangagwa doing?

On Monday Mr Mnangagwa, 76, broke off a trip to Europe to deal with the continuing unrest.

He had been due to attend the Davos economic summit where he was expected to seek investment for Zimbabwe.

Back in Harare, he took to Twitter to urge all sides to work together to fix a broken economy.

In a series of tweets, he said violence or misconduct by security forces was “unacceptable and a betrayal of the new Zimbabwe”, adding: “If required, heads will roll.”

How did the protests start?

Mr Mnangagwa announced a steep increase in the fuel price earlier this month.

The price rises were meant to tackle fuel shortages, but mean that Zimbabwe now has the most expensive fuel in the world, according to GlobalPetrolPrices.com.

Many Zimbabweans, worn down by years of economic hardship, have suddenly found they cannot even afford the bus fare to work.

This led to angry protests in Harare and the south-western city of Bulawayo.

Ellen Ngwenia, a pre-school teacher in Epworth, told the BBC: “I’m not afraid to protest, because we are hungry.”

Her mother, the school’s headteacher, was killed in last week’s protests after being hit by an army truck.

Teacher Ellen Ngwenia insists she will carry on protesting

Ms Ngwenia, who blames the government for her mother’s death, said “we will continue protesting until things [are] settled.”

Who does the government blame for the violence?

It accuses the opposition MDC party of using the protests for political means.

Presidential spokesman George Charamba said on Sunday: “The MDC leadership has been consistently pushing out the message that they will use violent street action to overturn the results of [last year’s] ballot.”

The opposition rejected a court ruling in August 2018 that confirmed President Mnangagwa had defeated MDC leader Nelson Chamisa

What has the opposition said?

The MDC said on Tuesday that five of its MPs had been detained and refused bail.

Party official Morgen Komichi dismissed Mr Mnangagwa’s announcement of an investigation into security forces, saying: “We don’t trust his word. We don’t regard him as an honest leader.”

The Zimbabwe Congress of Trade Unions, the umbrella group that called the protests, says its leader, Japhet Moyo, has also been arrested.

Mr Chamisa told the BBC there was “no justification whatsoever of having soldiers with live ammunition, with guns, machine guns, AK47 on the streets, beating up citizens”.

“People are being approached in their homes, they are being taken out of their homes with their families even if they are sleeping… a lot of people have been arrested for no apparent reason,” he said.